1. Field of the Invention
The invention relates to a method for operating a hybrid drive in a vehicle with an internal combustion engine and at least one electric machine connected thereto which is in connection with an energy storage device. The invention further relates to a method for determining differences in compression in a multi-cylinder internal combustion engine which is mechanically rigidly connected with a preferably variable-speed electric induction machine. The invention further relates to a method for operating an internal combustion engine, especially a hybrid vehicle which comprises at least one exhaust turbocharger and at least one oil pump. The invention further relates to a method for operating a vehicle which comprises a serial hybrid drive train with at least one internal combustion engine and at least a first and second electric machine, with the first electric machine being operated in the manner of a generator by the internal combustion engine in at least one operating range and the second electric machine driving at least one drive wheel of the vehicle in a direct or indirect manner.
2. The Prior Art
A control system for a hybrid vehicle is known from JP 2003-041966 A, in which the internal combustion engine compensates a torque loss of the electric machine when the electric machine is not ready for operation.
The electric machine of a hybrid shall increase driving power in many cases by positive moment (boosting function). The reproducibility of this function is problematic, especially in the case that the energy storage device is depleted or the electric machine is unable to provide its maximum output, e.g. due to overheating. In known systems, such situations will lead to drops in performance of the vehicle drive which the driver may neither foresee nor understand.
The compression of the cylinders is conventionally measured via the spark plug or glow plug bores. This is relatively time-consuming because spark plugs or glow plugs need to be removed prior to measurement.
A device for testing an internal combustion engine is known from JP 60256029 A2. The internal combustion engine is driven by an electromotor and the drive torque is measured.
JP 60256028 A2 and JP 60256027 A2 also disclose similar methods. The amount of the frictional resistances is derived on the basis of the measured torque.
Especially in the case of hybrid vehicles with an internal combustion engine with turbocharger, the lubrication of the turbocharger is critical during the switch-off process of the internal combustion engine after an operating phase with high speed (e.g. in so-called start-stop operation) because the oil pump, which is driven by the internal combustion engine for example, will no longer convey any lubricating oil after switch-off although the turbocharger can still run at high speed.
A control device for the generator of an electric vehicle is known from JP 2003-134608 A2, with the operating range of the vehicle being distinguished in manned and unmanned operation. In manned operation, the generator is stopped as soon as a predetermined loading state of the battery has been reached. In unmanned operation, the generator is driven in such a way that it will supply the more current to the battery the lower its loading state is.
JP 2003-134607 A2 describes a similar method.
In the case of vehicles with serial hybrid drive train, the internal combustion engine is operated with constant nominal speed for driving the first electric machine. This allows high efficiency, low consumption and low emissions. Such vehicles are used for example in the operation of public-transit buses. The disadvantageous aspect is that especially during the standstill of the vehicle in the area of the bus stops for example there will be a relatively high noise development by the internal combustion engine.
It is the object of the invention to avoid such disadvantages and to improve the drive behaviour of a hybrid vehicle. It is also the object of the invention to provide a method with which the compression of the individual cylinders can be determined with as little effort as possible. It is a further object of the invention to enable sufficient lubrication of the turbocharger during the cut-off process. It is further an object of the invention to reduce the noise emissions in vehicles with serial hybrid drive trains.